Mobile platforms having a plurality of fuel tanks often need to balance the fuel levels between the various fuel tanks to evenly distribute, or balance, the weight of the fuel in each fuel tank. For example, an aircraft with a fuel tank in each of the main wings will endeavor to maintain approximately equal fuel levels in each tank to improve ease of control, safety and fuel efficiency of the aircraft during flight. Although it will be understood that the term “mobile platform” as used herein refers to various applicable mobile platforms such as buses, trains, ships and aircraft, the exemplary references made throughout the present application will be made with reference to aircraft. However, it will further be understood that the reference to aircraft is merely exemplary and not to be construed as limiting the scope of the invention to aircraft only. Rather, the invention relates to any and all mobile platforms having a plurality of fuel tanks where balancing the fuel levels in the fuel tanks is desirable.
Additionally, the operation of many mobile platforms is governed by various state and federal regulations. For example, with reference to aircraft, in order to show compliance with regulations, it must be shown that if one engine needs to be shut down during flight, referred to as an in-flight shutdown (IFSD) event, enough fuel is available to the remaining engine to reach a diversion airport. Therefore, such mobile platforms typically implement fuel systems that have a dual crossfeed configuration that fluidly connects the two or more fuel tanks. Therefore, fuel can be consumed from any fuel tank through a crossfeeding fuel transmission structure, e.g., a crossfeeding piping system. More particularly, the dual crossfeed configuration includes two different fuel crossfeed paths such that the failure of either crossfeed path in conjunction with an IFSD event does not jeopardize the safe operation of the aircraft.
Known crossfeed configurations often employ redundant fuel piping and valve equipment that performs no other purpose than redundancy. Having such additional redundant equipment is an inefficient use of resources on the mobile platform. Other known crossfeed configurations on aircraft incorporate a single crossfeed system and a separate gravity-flow redundant, i.e., backup, transfer system that requires the flight crew to activate the system and sideslip the aircraft to induce flow in the correct direction. This requires elaborate procedures that increase pilot workload. Still other known systems use dedicated transfer pumps and piping to transfer fuel from one tank to another, i.e., transfer fuel from the ‘high level’ tank to the ‘low level’ tank. Additionally, some such systems are know to be fully automated whereby the fuel transfer takes place without initiation, monitoring or any other involvement or action by the mobile platform operator, e.g., a pilot of an aircraft. These known systems comprise additional equipment, which is an inefficient use of mobile platform resources.
Therefore, it would be desirable to implement a mobile platform fuel system that meet applicable regulations with reduced weight, reduced manufacturing and maintenance costs, that does not increase crew workload and provides an acceptable interface to the crew.